Marathon des Sables: Inner Workings

It is possibly the most deceivingly named race on the planet. Over seven days and six stages, participants in the Marathon des Sables run, stumble, burn, stink, hallucinate, cry and bleed across 156 miles of the Sahara Desert in Morocco. They carry all their gear and food, obey a laundry list of safety rules, sleep in communal tents, and blister their feet down to the fascia. For this privilege, racers sign up two years in advance and pay £3,200 (for 2011). They crave the challenge: "It boils life down to a balancing act of mind, body and environment," says Meghan Hicks of Midpines, California, who placed second female in 2009. Simply finishing is an epic achievement. Here's how the race is run...

1. Food to Go

Runners must carry at least 14,000kcal (about 4.5kg) worth of food and drink mix; however, all but the smallest runners will need much more than that, says Ron Maughan, a sports nutrition professor at Loughborough University. For  example, a 10st 10lbs racer requires 2,860kcal during a marathon-length stage, on top of the 2,000kcal to fuel his day, and the 500kcal to feed his elevated metabolic rate.

2. Big Foot

Heat edema causes feet to swell, so runners must wear shoes one half to two sizes larger than normal. “The body’s natural cooling response dilates your blood vessels and sends more fluid to your extremities,” says Ronald Otterstetter of the University of Akron in Ohio, US. “But because of gravity, your heart is unable to pump fluid back out of your feet.”

3. Rough Stuff

To keep sand out, runners often sew or Velcro gaiters to their shoes. Sand sticks to anti-chafing lubes and the friction can turn thigh skin into sandpaper. Compression shorts eliminate this.

4. Sun Screening

Temperatures can top 50C. Runners don legionnaire hats and sweat-wicking apparel, hydrating regularly to keep their body temperature down. Salt tablets balance electrolytes (low levels weaken muscle contractions and cause cramps).

5. Water Fix

To maintain competitive equality, runners get 1.5 litres in the morning, and 1.5-4.5 litres at checkpoints every five to nine miles during each stage. (You need two to four times the amount of water when running 26.2 in the desert compared with running the London Marathon, says Maughan.) At night, racers get 4.5 litres. This ration covers drinking, meals and washing up.

6. Travel Light

Backpacks must weigh between 6.5kg and 15kg, including food (but excluding water). This ensures racers carry the caloric minimum and the mandatory desert survival gear (listed below), while reducing injury risk from too-heavy loads. The day before the race, officials weigh each pack and check for required supplies.